In rotary regenerative heat exchange apparatus a mass of heat absorbent material commonly comprised of packed element plates is first positioned in a hot gas passageway to absorb heat from hot gases passing therethrough. After the plates become heated by the hot gases they are moved to a passageway for air or other cool fluid where the then hot plates transmit their absorbed heat to the fluid passing therethrough.
The heat absorbent material is carried in a rotor that rotates between hot and cool fluids, while a fixed housing including sector plates at opposite ends of the rotor is adapted to enclose the rotor. To prevent mingling of the hot and cold fluids, the end edges of the rotor are provided with flexible sealing members that rub against the adjacent surfaces of the rotor housing to accommodate a limited amount of rotor "turndown" or other misalignment caused by mechanical loading or thermal deformation of the rotor and the rotor housing.
To permit turning the rotor freely about its axis, certain minimum clearance space between the rotor and adjacent rotor housing is desired, however, excessive clearance is to be avoided because it will dictate excessive fluid leakage. Sealing means that compensate for the opening of space between the rotor and rotor housing are provided by U.S. Pat. Nos. 3,786,868 and 4,124,063. In these patents the sector plate is moved to what is believed to be an optimum position adjacent the end of the rotor so there will be a minimum of leakage between the sector plate and the adjacent rotor. Although such an arrangement is theoretically desirable, an effective way of rapidly sensing the precise movement desired by the sealing means or sector plate has not been developed so that corrective measures may be effected.